1. Field of the Invention
The invention relates to assemblies for interconnecting AC generators and AC powered systems, and for converting solar energy to AC electrical power, and to electrical connector and cable harness means for interconnecting components of such assemblies.
2. Description of the Prior Art
Assemblies for converting DC sources of electrical energy, such as solar cells, batteries, and the like, to readily usable AC electrical power are known. However, current systems, particularly in the solar energy area, comprise a variety of components from multiple manufacturers. Such components in the solar energy area include photovoltaic cells, commonly referred to as solar cells, which convert solar energy to DC electrical power. Such cells are generally grouped in supporting and protective photovoltaic modules which are customarily mounted on roof tops, or other such structures, exposed to sunlight. The photovoltaic cells, and therefore, the photovoltaic modules, produce DC electrical power.
Usually, a number of photovoltaic modules are connected to an inverter which converts DC power output of the photovoltaic modules to AC power.
Photovoltaic systems usually include multiple DC photovoltaic modules connected in one or more series, or strings, feeding an inverter, which converts DC power to AC power. This system suffers from inefficiencies, such as module-to-module mismatch and power loss due to varying module orientations and significant shading losses. To connect one or more photovoltaic modules together to form a module string, there is provided a module cable harness including transmission wires and connector portions. A plurality of module and inverter strings may be connected to an AC buss by a module cable harness. The AC module buss may be connected to a junction box by a further cable harness with appropriate connector means.
The above described building blocks for photovoltaic power generating systems thus include DC generating photovoltaic modules, DC to AC inverters, DC and AC switches and other mechanical and electrical components.
Past AC modules have connected to a utility grid by utilization of an AC module cable harness which links AC module to AC module, functioning as both an AC physical string and an AC electrical buss.
The bussing of AC modules onto an AC power buss maintains the same AC voltage while it incrementally increases current with each AC module added. One or more strings/busses of AC modules are then connected to a combiner junction box to transition from the AC module cable harness to a runback wire to the service panel. The combiner junction box provides a terminal for transitioning the combined busses to a larger wire gauge and, optionally, overcurrent protection for each of the two AC busses.
The current state of the art for an AC module cable harness uses two, three-wire, quick connectors in the form of a male and female part and a three-wire cable connecting them. A single phase 120 volt AC module micro-inverter connects to the three-wire cable to make up the AC module buss. The micro inverter connects to line, neutral, and ground on the AC module buss.
In the current state of the art for two AC module strings connected to a combiner junction box, the two strings each are an AC module buss with a maximum of n modules. A standard AC module with a straight-through AC module cable harness connects to a combiner junction box in the center of two AC module strings of n modules.
AC modules must operate at the voltage of the grid to which they are interconnected. Typical USA residential and commercial grid services have available single-phase 120V, three-phase 120/208V, or split-phase 120/240V AC. It is desirable to have a product is operable on a 120V AC single phase line, because it is a universally available service voltage. In a residence, there is typically a split-phase 120/240V AC service available, consisting of two line conductors and a single neutral. The voltage between line and neutral is 120V AC. For typical commercial settings there is a three-phase 120/208V AC service that consists of three lines and a neutral. In this case, the voltage between a line and neutral is also 120V AC.
It also is desirable to connect as many AC modules on a single AC module string as possible, thereby avoiding additional junction boxes and service panel runback wires. In addition to adding cost, the junction box may require a roof penetration or may require a visible metal clad conduit, which installers try to minimize because of roof warranty issues and aesthetics.
The maximum number of AC modules on a buss depends on the AC module current rating, wire gauge and wire temperature rating. Higher temperature ratings and larger wire gauge increase the cost of the AC module cable harness. Therefore, as n increases, the cost of the AC module cable harness increases.
A limitation of the current AC module physical layout is that the junction box must be placed in a physical location that assures that it will accommodate the desired physical layout and electrical requirements of the AC module string.